The present invention relates to an electrode structure on a matrix type liquid crystal display panel.
In recent years, a substantial amount of effort in the field of liquid crystal matrix displays has been devoted to providing a high-density multi-line display, aiming at an improvement in image quality. Liquid crystal displays with matrix shaped electrode structures are quite favorable to fulfilling a power saving demand because of their capability of being excited with low power consumption.
A conventional drive technique for such a matrix type liquid crystal display, for example, the line sequential drive method as shown in FIG. 1, has long been known. A main memory 1 stores characters, symbols, patterns or the like and an intelligence signal converter 2 converts data contained in the memory 1 into the associated display patterns. After those patterns are stored line by line into a buffer memory in a column driver 3, respective column electrodes Y.sub.1, Y.sub.2, . . . Y.sub.n are supplied with those patterns. Row electrodes X.sub.1, X.sub.2, . . . X.sub.m crossing the column electrodes, on the other hand, are sequentially enabled through a row driver 4, thereby displaying information contained in the buffer memory in a line-by-line fashion. A control 5 provides an operation control for the row and column driver circuits. A liquid crystal display with a matrix type electrode structure is labeled 6.
For the matrix type liquid crystal display panel, the greater the number of the rows (scanning line number) the higher the density and accuracy of display. However, with an increase in the number of the rows, the length of time at which a signal is applied per column, i.e., duty factor, is shortened and the problem of crosstalking arises. In particular, liquid crystal display panels show dull threshold characteristics and slow response characteristics, making it difficult to assure satisfactory contrast. There have been several attempts to overcome the problem, including:
(1) The development of liquid crystal material having more definite threshold properties;
(2) A matrix address scheme in the optimum condition with an extended operating margin (.alpha.=V.sub.on /V.sub.off); and
(3) The design of an electrode structure with a seemingly higher resolution.
Though the first two attempts (1) and (2) do not require modifications in the well known structure of liquid crystal cells, it appears almost impossible to increase drastically the number of excitable lines from the viewpoint of the present-day progress of liquid crystal materials, etc. Contrarily, the problem with the last method (3) is that the liquid crystal cells are sophisticated in construction but, it is actually possible to increase the number of excitable lines by a factor of two or more.
Typical ways of making possible the last approach (3) are as follows:
(a) double electrode structure
(b) vertical partition, and
(c) two-layered structure.
These methods may be adopted alone or in combination for achieving the intended purpose. Such a combination has been proposed by co-pending application Ser. No. 921,062 June 30, 1978, MATRIX TYPE LIQUID CRYSTAL DISPLAY PANEL by F. Funada et al, now U.S. Pat. No. 4,231,640.